Not Applicable.
Not Applicable.
This invention relates to a polymeric hydrogel drug delivery system for absorbed antiglaucomatous medications which can be delivered into the ocular fluid.
Glaucoma is a progressive optic neuropathy characterized by a specific pattern of damage to the head of the optic nerve and visual field. The visual system in glaucoma is damaged by the death of nerve cells which carry the visual impulse from the eye to the brain. Once a sufficient number of nerve cells are destroyed, blind spots develop, usually beginning in the peripheral field of vision. Eventually central vision is affected. Since no treatment exists to restore these damaged nerve cells, this visual loss is irreversible. glaucoma cannot currently be cured, but can be effectively managed by medical or surgical treatment.
The single most important risk factor known for the development and or progression of glaucomatous damage is elevated intraocular pressure (IOP). Average IOP ranges between 14-22 millimeters of mercury (mmHg). A pressure of of 22 or greater is considered to be elevated. Persons with IOP of 22 or greater are carefully monitored and receive treatment to lower their IOP. In some individuals with elevated IOP no ocular damage can be detected, nonetheless, they receive treatment to restore IOP to the normal range.
Numerous ocular drug delivery systems have been developed to manage IOP, but the complex anatomy of the eye have limited their effectiveness. Medications introduced into the eye are quickly washed out of the pre corneal area by the rapid production of lacrimal fluid. Additionally, medication in the eye is poorly absorbed because of the low permeability of corneal tissue.
Currently, dosing with ophthalmic medications in the form of drops results in a pattern of brief overdose of the eye medication when the drop is initially instilled, followed by a relatively short period of therapeutic dosing, followed by an interval in which the medication level drops to a less than therapeutic value. It has been determined that the ocular side effects and the more serious systemic side effects of ophthalmic drugs are primarily related to this period of initial drug overdose.
Systemic side effects experienced by the users of beta-adrenergic blocking drugs such as timolol maleate have included cardiac arrhythmias, life threatening bronchospasm and stroke. Therefore the use of beta-adrenergic blocking agents to treat glaucoma in patients diagnosed with significant cardiac or pulmonary disease requires careful monitoring and is often precluded altogether.
Additionally, a problem in the field of glaucoma treatment is the development of resistance to the commonly used anti-glaucoma medications by patients who eventually require increasing doses of their current medications or the addition of new medications to control IOP.
Ointments, gels and high viscosity eye drops have been used to provide a longer acting formulation for anti-glaucoma medication. But these delivery systems have caused significant blurring of vision and ocular discomfort in many of those patient who have tried them. Ocular inserts have also produced substantial discomfort and often fall out of the eye of their users, after which they cannot be used again.
Another concern in the area of glaucoma treatment is the issue of patient compliance with prescribed treatment programs. Often topical delivery systems involve complicated, repetitious dosing schedules and the use of gels or drops which can be awkward and difficult to apply.
The use of conventional hydrogel contact lenses containing various medications is known in the art. However, it is not known to treat elevated intraocular pressure with dilute concentrations of timolol maleate or brimonidine tartrate which have been passively transferred in an aqueous solution to hydrogel contact lenses which were prepared by washing in saline and then briefly drying the lenses.
It is known to simply presoak soft contact lenses such as Soflens (copyright) manufactured by Bausch and Lomb, in pilocarpine hydrochloride. However, some studies have found that this lens medicament delivery system may be unsuitable for use because the lens releases 100% of pilocarpine hydrochloride in buffered saline and distilled water in merely 1.5 and 2.5 hours respectively as disclosed in U.S. Pat. No. 4,731,244. Furthermore, while it is known in the art to simply presoak contact lenses in drug solutions, these medications commonly contain preservatives such as benzalkonium chloride, which have a greater affinity for the hydrophilic contact lens material than do the aqueous drug solutions, with the result being the production of lenses with concentrated levels of preservative which can be toxic to the corneal epithelium. (Bawa, R. Chapter 11, Ocular Inserts p.231 citing Hillman, J. S. Br.J.Opthal., 58(7):674 (1975)
In view of the many disadvantages of these prior medication delivery systems, there is still a need for a new ophthalmic medication delivery system.
It is the object of this invention to provide an ophthalmic medical agent delivery system by utilizing a polymeric hydrogel to which a dilute anti-glaucoma medication has been passively transferred and from which this medication will be gradually delivered, providing the ocular environment an extended period of contact with this absorbed medication.
This invention relates to a polymeric composition comprising a polymeric hydrogel material containing an anti-glaucoma medication, either a solution of timolol maleate in a concentration of less than 0.25% by weight or brimonidine tartrate in a concentration of less than 0.2% by weight as an additive absorbed in the polymeric composition and transferable therefrom. The polymeric hydrogel composition containing the passively transferred anti-glaucoma medication is most useful as a contact lens. The lenses which function most effectively in this instance are those that are hydrogels containing about 38-60% water by weight. All percentages described in the present invention are by weight unless otherwise specified.
This invention further relates to a process for preparing a hydrogel contact lens for use which comprises saturating the lens in a physiologic saline solution; drying the washed lens briefly and then placing the partially desiccated lens into an aqueous solution of diluted medicament at a pH of about 7.0-7.4 for approximately 3 hours and then removing the medicated lens from solution ready for use in the ocular environment.
It is an object of this invention to provide an ophthalmic medication delivery by utilizing a polymeric hydrogel which will provide effective control of elevated IOP by utilizing diluted doses of timolol maleate or brimonidine tartrate which will be delivered to the ocular environment for a period of time longer than the current dwell time achieved by these medications when used in their presently known drop or gel formulations.
It is a further object of this invention to effectively manage elevated IOP by utilizing timolol maleate or brimonidine tartrate in dilute doses which will therefore decrease the probability that users would develop resistance to these drugs and would subsequently require increased doses or substitute medications to control IOP.
Another object of this invention is to provide an ophthalmic medication delivery system of dilute timolol maleate or brimonidine tartrate to the ocular environment which will effectively control elevated IOP, but in doses lower than those at which they are currently formulated as drops or gels to reduce the risk of systemic or ocular side effects from these drugs. This diminution in the risk of systemic side effects will enable the utilization of timolol maleate or brimonidine tartrate in some of those patients who would have been precluded from their use because of existing cardiac or pulmonary conditions.
Still another object of this invention is to provide an ophthalmic medication delivery system for dilute anti-glaucoma medications which can be administered as a single daily dose, The convenience and simplicity of this system will enhance patient compliance with antiglaucomatous therapy.
An additional object of this invention is to provide an ophthalmic medication delivery system utilizing polymeric hydrogel lenses soaked in dilute formulations of antiglaucomatous medications to produce lenses which have absorbed an effective amount of medication without being exposed to higher levels of preservatives which are presently found in the medications at their currently known doses. These lenses will therefore absorb preservatives such as benzalkonium chloride in greatly reduced amounts which will then eliminate complications arising from preservative induced corneal toxicity.